Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe
DF: Fachverband Dielektrische Festkörper
DF 2: Dielectric Spectroscopy & Microscopy
DF 2.1: Vortrag
Montag, 23. März 2009, 10:40–11:00, WIL A317
Space-charge wave spectroscopy of hexagonal silicon carbide — •Michaela Lemmer, Burkhard Hilling, and Mirco Imlau — Department of Physics, University of Osnabrück, Osnabrück, Germany
Space-charge wave (SCW) spectroscopy is based on resonant
excitation of SCW in a semi-insulating material, for instance,
high resistive semiconductors. This promising new technique allows
to examine important photoelectric parameters of a wide variety of materials.
Here, hexagonal silicon carbide with 4H and 6H stacking sequence
has been investigated by SCW spectroscopy. For SCW excitation, the
sample is exposed to a light pattern oscillating around an
equilibrium position. This is realized with a two-beam
Mach-Zehnder interferometer, where one of the beams is
sinusoidally phase-modulated with an electro-optic
phase-modulator. The dispersion behaviours found for the 4H sample
indicate the existence of trap recharging waves and yield
the product of mobility and lifetime µ τ and the
effective trap density Neff. The data set of the 6H
polytype indicates a comparably smaller effective trap density,
but an unambiguous assignment to the existence of trap recharging
waves fails. Taking into account the general classification of
material parameters which provides the existence for SCW, the
particular case of damped, forced charge-density
oscillations can be concluded.
Financial support from the Deutsche Forschungsgemeinschaft (DFG,
project Nos. GRK 695 ”nonlinearities of optical materials”) is
gratefully acknowledged.